Calendering and slitting

A dry electrode contains active particles, conductive additive, binder, and pores. Calendering rearranges particles, increases contacts, narrows pore-size distribution, and may deform soft particles or fracture brittle ones. Electronic pathways and volumetric energy often improve, while tortuosity, wetting, and through-thickness transport may worsen. Assess compaction with thickness, areal loading, compacted density, porosity, peel strength, resistance, and rate under matched material and loading.

Layered oxides, Prussian blue analogues, polyanionics, and hard carbon differ in morphology, hardness, porosity, and surface state. Low-density PBA particles may be more damage-prone, hard-carbon morphology and binder affect springback, and dry electrodes have a different fibrillated network from wet electrodes. Roll temperature, speed, and multiple passes alter stress relaxation. Development needs a relationship among pressure or gap, thickness, springback, and electrochemistry rather than treating equipment settings as material-independent.

Cross-web force, roll temperature, and thickness may be nonuniform, while beginning, middle, and end of roll vary as equipment stabilizes. After leaving the nip, binder network and particles spring back; temperature, humidity, and wait time change the remeasured thickness. One average misses edge and long-period variation. Use fixed locations and wait conditions, combining inline thickness, offline cross-sections, roll diameter, and tension to identify roll wear, thermal bow, and inherited coating variation. If the remeasurement rule changes, establish a new historical trend.

Rotary-knife or other slitting requires stable clearance, overlap, sharpness, tension, and dust extraction. Tool wear, brittle electrodes, or heavy edges generate metal burrs, coating shedding, and particles; width variation and wandering edges alter electrode overlap. Visual inspection alone cannot assess small metal protrusions. Combine microscopy, profile measurement, particle counting, and periodic sampling, recording tool life and defect location on the roll. Burr assessment also considers direction, separator coverage, and later compression.

Higher compaction can raise initial volumetric energy yet reduce rate or life through slow wetting, local polarization, and particle damage. Edge defects may appear during assembly and formation as resistance spread, self-discharge, or micro-shorts. Evaluation covers filling and wetting, formation, rates at different temperatures, cycling, and post-mortem analysis with statistical samples. Beginning, middle, end, and cross-web positions should be compared so an average does not hide local extremes. When material, loading, binder, or electrolyte changes, the previous calendering and slitting window needs revalidation.